Effects Of Process Variables Flashcards
Solid polymers that tend to form order regions.
Crystalline Polymers
Polymers that have no crystals at all.
Amorphous Polymer
True or False.
A real polymer can be crystalline, and the extent of crystallization is characterized by the percentage of crystallinity.
False. A real polymer is never completely crystalline.
In the amorphous region of the polymer, at lower temperature, the molecules of the polymer are in frozen state, where the molecules can vibrate slightly but are not able to move significantly.
Glassy State
When the polymer is heated, the polymer chains are able to wiggle around each other, and the polymer becomes soft and flexible similar to rubber.
Rubbery State
The temperature at which the glassy state makes a transition to rubbery state .
Glass Transition Temperature
The temperature where a diffuse transition zone between the rubbery and liquid states for crystalline polymers.
Flow Temperature
The glass transition temperature is the property of the amorphous region of the polymer whereas the crystalline region is characterized by ___________.
Melting Point Temperature
Enumeration.
Factors Affecting Glass Transition Temperature.
- Intermolecular Forces
- Chain Stiffness
- Cross-linking
- Pendant Groups
- Plasticizers
- Molecular Weight
True or False.
Weak intermolecular forces cause higher glass transition temperature (Tg).
False. Strong IMF causes higher Tg.
The presence of stiffening groups in the polymer chain reduces the flexibility of the chain, leading to _______ glass transition temperature.
Higher
Which is stiffer,
Polyethyleneterephthalate or Polyethylene Adipate?
Polyethyleneterephthalate, due to the presence of Benzene ring.
True or False.
Cross-links between chains restrict rotational motion and raise the glass transition temperature.
True
The presence of _______________, such as benzene ring, can restrict rotational freedom, leading to higher glass transition temperature.
Bulky Pendant Groups
The presence of _________________, such as aliphatic chains, limits the packing of the chains and hence increases the rotational motion, tending to less Tg value.
Flexible Pendant Groups
Low molecular weight and non-volatile materials added to polymers to increase their chain flexibility.
Plasticizers
True or False.
Plasticizes reduce the intermolecular cohesive forces between the polymer chains, which in turn decrease Tg.
True.
True or False.
The glass transition temperature is also affected by the molecular weight of the polymer. Tg increases with decreasing molecular weight.
False. Higher MW increases Tg.
The pressure exerted by a fluid at equilibrium at any point of time due to the force of gravity.
Hydrostatic Pressure
The pressure exerted by a liquid on a solid surface.
Hydrostatic Pressure
A unit of measurement of an object’s or substance’s resistance to being deformed elastically when a stress is applied to it.
Elastic Modulus
It describes the ratio of the change in length or volume of a material to the change in length or volume of the applied load.
Elastic Modulus
The force causing the deformation divided by the area to which the force is applied.
Stress
The ratio of the change in some parameter caused by the deformation to the original value of the parameter.
Strain
Describes tensile and compressive elasticity, or the tendency of an object to deform along an axis when opposing forces are applied along that axis.
Young’s Modulus
Describes an object’s tendency to shear when acted upon by opposing forces.
Shear Modulus or Modulus of Rigidity
It is defined as shear stress over shear strain.
Shear Modulus or Modulus of Rigidity
Describes volumetric elasticity, or the tendency of an object to deform in all directions when uniformly loaded in all directions.
Bulk Modulus
Describes the object’s tendency to flex when acted upon by a moment.
Flexural Modulus
Enumeration.
Types of Elastic Modulus.
- Young Modulus
- Shear Modulus
- Bulk Modulus
- Flexural Modulus
A material property and is the stress corresponding to the yield point at which the material begins to deform plastically.
Yield Strength
The appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress.
Fracture
Displacement develops perpendicular to the surface.
Normal Tensile Crack or simply Crack
Displacement develops tangentially.
Shear Crack, Slip Band, Dislocation
The stress at which a specimen fails via fracture.
Fracture Strength or Breaking Strength
A substance that accelerates chemical reactions without being consumed in the process.
Catalyst
A quantity that measures the extent to which the reaction has proceeded.
Extent of Reaction
In polymers, it refers to the degree of crosslinking or bonding between the monomers in a polymer chain.
Extent of Reaction
A general expression, relating average functionality, extent of reaction, and average degree of polymerization for polycondensation reaction carried out for a period.
Carother’s Equation
Defined as the fraction of functional groups/monomers that have reacted at time t.
Extent of Reaction
Defined as equal to the total number of bifunctionality initially added, No, divided by the remaining number of molecules N after time t.
Average Degree of Polymerization
